1. Field of the Invention:
This invention relates to a differential gear and, more particularly, to a differential gear used in a drive line of a vehicle to drive front or rear wheels and a center differential gear of a four wheel drive car.
2. Description of the Prior Art:
When one of two wheels connected to a drive line having a differential gear runs on a snow-covered road surface or the like having a low coefficient of friction and such wheel then slips, a phenomena occurs such that the driving force to other wheel connected to the drive line is reduced or utterly lost because of the inherent property of said differential gear.
A similar problem applies to a center differential gear installed to absorb a differential number of revolutions between front and rear wheels on a full time four wheel drive car in turning. Thus, there is proposed a special differential gear with a differential lock or a limited slip differential.
Since the special differential gear needs the differential lock or limited slip differential, the construction of the special differential gear is complicated.
When the special differential gear is provided with the differential lock, a driver has complexities that he or she has to lock and unlock the differential lock, and moreover there is a possibility of dangerous wrong operation to lock it in turning.
When the limited slip differential is incorporated in the special differential gear, the driving force transmitting capacity is structurally limited. In this case, a sufficient driving force cannot be transmitted.